Magnetic sensor for defects utilizing split ring coils and having means for draining scale therefrom

ABSTRACT

The present invention relates to devices for determining defects in rolled products and tubes and, more particularly, the invention relates to electromagnetic apparatus for detecting defects in rolled products and tubes installed in production lines of rolling mills and tube-welding units. The invention consists in that the transducer of the apparatus is provided with three individually mounted turns, one of which is used as an inductor, while the other two are disposed at both sides of the inductor coaxially thereto and are connected differentially.

ilnited States Patent m1 Lovlya et al.

['45] Mar. 27, 1973 [54] MAGNETIC SENSOR FOR DEFECTS UTILIZING SPLIT RING COILS AND HAVING MEANS FOR DRAINING SCALE THEREFROM [76] Inventors: Andrei Dmitrievich Lovlya, ulitsa Stalevarov, 4b, kv. 39; Igor Illarionovich Kazakevich, prospekt Lenina, 28, kv. 44; Nikolai Ivanovich Gribalev, ulitsa Sotsialisticheskaya, 22/II, kv. 6; Vladimir Mikhailovich Lozhkin, ulitsa Pobedy, 20, korpus 4, kv. 37, all of Elektrostal, Moskovskoi oblasti; Boris Ivanovich Sokolov, ulitsa Lunacharskogo, 6; Sergei Fedorovich Safronov, prospekt Lenina, 27, kv. 8, both of Noginsk, Moskovskoi oblasti; Evgeny Vasilievich Morozov, ulitsa Kommunisticheskaya, 24, kv. l8, Polerskoi, poselok Seversky, vSverdlovskoi oblasti; Vladimir Andreevich Sirota, prospekt Lenina, 23, kv. 46, Elektrostal, Moskovskoi oblasti; Vladimir Andreevich Mitkin, prospekt Lenina, 31, kv. 46, Elektrostal, Moskovskoi oblasti; Nikolai lvanovich Kozhin, ulitsa Gorkogo, 24, kv. 58, Elektrostal, Moskovskoi oblasti; Anatoly Dmitrievich Bratus, prospekt lenina, 26, kv. 2, Elektrostal', Moskovskoi oblasti, all of USSR.

22] filed? Mar. 29, 1971 Appl. No.: 128,859 a-..

[52] US. Cl ..324/37 [51] Int. Cl. ..G01l 33/12 [58] Field of Search ..324/37, 40

[56] References Cited I UNITED STATES PATENTS 3,271,664 9/1966 Mountz et al. ..324/40 FOREIGN PATENTS OR APPLICATIONS 991,890 5/1965 Great Britain ..324/40 OTHER PUBLICATIONS Magnaflux Corp., Electromagnetic Eddy CurrentTesting; Manaflux Corp. Publication, 1965, 4 pages Primary ExaminerRobert J. Corcoran Attorney-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT Thepresent invention relates to devices for determining defects in rolled products and tubes and, more particularly, the invention relates to electromagnetic apparatus for detecting defects in rolled products and tubes installed in production lines of rolling mills and tube-welding units.

The invention consists in that the transducer of the apparatus is provided with three individually mounted turns, one of which is used as an inductor, while the other two are disposed at both sides of the inductor coaxially thereto and are connected differentially.

1 Claim, 7 Drawing Figures Patented March 27, 1973 4 Sheets-Sheet 1 n wt Patented March 27, 1973 3,723,860

4 Sheets-Sheet 2 Patented March 27, 1973 4 Sheets-Sheet 5 Patented March 27, 1973 3,723,860

4 Sheets-Sheet 4 AMPLITUDE PHASE ELECTRONIC OUTPUT DISCRIMINATOR AMPLEFIER DEVICE SEARCH con Y )1 CONTROL APPARATUS\ FEAT W B Q SIGNAL F J L I l i POWER SUPPLY L H 5 j'urm AUDIO-FREQUENCY T- 270 v GENERATOR 7 MAGNETIC SENSOR FOR DEFECTS UTILIZING SPLIT RING COILSAND HAVING MEANS FOR DRAINING'SCALE THEREFROM tecting defects in rolled products and tubes comprisinga pass-through type detector and a coil for magnetizing the tested sections of rolled products and tubes (c.f. us. Pat. No. 3,271,664).

This patent discloses an electromagnetic apparatus comprising a coil for magnetizing the controlled sections of rolled products and tubes and a pass-through type transmitting transducer located within the coil and used for exciting a high-frequency field and eddy currents in the sections of the rolled products and tubes and forproducing a signal sensitive to the above-said field and eddy currents. In the known apparatus the transducer is provided with three multiturn coils which are wound on a dielectric sleeve.

However the known electromagnetic apparatus practically can not be used directly in production lines of rolling mills and tube-welding units under conditions of continuous action of water, emulsion vapors, temperature, scale particles falling from the test pieces, etc. These unfavorable effects upon the transducer with three multiturn windings result in a breakdown of the insulation of the coils and premature failure of the apparatus. The apparatus with the multiturn windings also does not permit the electromagnetic fields to be adequately localized so as to increase the sensitivity of the apparatus to defects of rolled products and tubes having a small length as well as to reduce the length of the uncontrollable ends of the rolled products and tubes.

An object of the present invention is to provide an electromagnetic apparatus for detecting defects in rolled products and tubes which would be reliable in operation, when mounted directly in a metallurgical line for making rolled products and tubes under the action of high temperature, vapors, scale, emulsion and water.

Another object of the invention is to provide such an apparatus, in which the transducer for exciting a highfrequency field and eddycurrents within the tested sections of the rolled products and tubes and for generating a signal sensitive to said field and currents would make it possible to reduce the length of the uncontrollable ends of the rolled products and tubes and to increase the sensitivity of the electromagnetic apparatus to the local defects.

Still another object of the invention is to provide such an electromagnetic apparatus of the type described which would have a simple construction and would allow the transducer to be easily replaced.

Other objects and advantages of the invention will be apparent from a consideration of the following description and the accompanying drawings. I

These and other objects of the invention are attained due to the fact that in the electromagnetic apparatus for detecting defects in rolled products and tubes com prising a pass-through type transducer and a coil for magnetizing the controlled sections of the rolled products and tubes, according to the invention, the transducer has three individually mounted coils, one of which serves as an inductor, while the other two are located at both sides of the inductor coaxially therewith and are connected differentially.

The coils are preferably made of rigid split rings disposed within a framework of a dielectric material, in which case the ring coils connected differentially are equal in size and have the same electric characteristics, while the diameter thereof is smaller than that of the third ring coil connected as an inductor.

The framework is preferably made of coaxially disposed ring-shaped disks, the outer faces of which are provided with annular grooves for accomodating the smaller coils and which have a central inner groove for disposition of the larger coil, a through slot being provided in the lower portion of the framework for passing the scale,'water and emulsion falling from the rolled products and tubes.

It is expedient that the coaxially mounted disks containing the coils are interlinked through at least four current-carrying contact bushes two of which are connected to the terminals from the inductor coil and the other two are connected to the terminals from the differential coils and are secured within the apparatus by means of contact pins passed through the above-said current-carrying bushes.

Due to realization of the present invention there is provided an apparatus for detecting defects in rolled products and tubes, which when used directly in the lines of rolling mills and tube-welding devices, is featured by high reliability and a long life. This apparatus has a higher sensitivity to thelocal defects and makes it possible to reduce the length of the uncontrollable sections at the ends of the rolled products and tubes.

The invention is further described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a partial sectional view of the apparatus according to the invention;

FIG. 2 is a sectional view taken along the line "-11 in FIG. 1;

FIG. .3 is a side view of the electromagnetic apparatus according to the invention shown along arrow (A111 FIG. 4 is a transducer of the electromagnetic apparatus according to the invention;

FIG. 5 is a sectional view taken along the line VV in FIG. 4;

FIG. 6 is a sectional view taken along the line VI-VI in FIG. 4;

FIG. 7 is a block diagram of the electromagnetic apparatus according to the invention.'

The proposed electromagnetic apparatus for detecting defects in rolled products and tubes comprises a transducer 1 (FIG. 1) of the pass-through type with a first coil 2. I

In order to reduce the noise level during the detection of the defects of the controlled articles and to obtain maximum localization of the electromagnetic field, therefore, to increase the sensitivity of the apparatus to small defects of the tested articles, the transducer I has three further individually mounted coils 3,4 and 5 (FIGS. 1 and the second coil 3 of which is connected as an inductor, while the other two coils 4 and 5 serve as measuring coils and are connected differentially.

For increasing the reliability and durability of the apparatus during the operation under the action of water, emulsion vapors, falling scale and high temperature, each of the coils 3,4,5 is made of a rigid, mechanically calibrated split ring and is mounted in a framework 6 (FIGS. 5,6) made of a dielectric material and having a through slot (window) B which extends in a radial direction (FIGS. 4,5).

To simplify the mounting of the coils 3,4,5, the framework 6 is made of coaxially installed disks 7,8 with annular grooves C and D for accomodating the coils.

Thus, the ring second coil 3 is mounted within the grooves C of the disks 7 and 8, while the ring third and fourth coils 4 and 5 are disposed in the grooves D of the disks 7 and 8 respectively. At the end faces of the framework'6 the coils 4 and 5 are closed with covers 9 and 10 made ofa dielectric material.

In order to reduce the time of readjustment of the apparatus, when changing the size of the articles to be controlled the coaxially mounted disks 7 and 8 accomodating the ring coils 3,4,5 are interlinked through four current-carrying bush contacts 11, 12, 13 and 14 (FIG. 4). Two bushes 11 and 12 are connected to the terminals 15 and 16 from the ring coil 3 connected as an inductor. The other two bushes 13 and 14 are connected to the terminals 17 and 18 of the differentially connected individual ring coils 4 and 5. The interlinked disks 7 and 8, in turn, are mounted in the apparatus with the help of contact pins 19 (FIG. 2) passed through the current-carrying bushes 11, 12, 13 and 14 and with the help of nuts 20.

The pins 19 are cantilevered in a dielectric 21 which is fixed to the housing 22 of the apparatus by means of screws 23.

The housing 22 is provided with guards 24 and 25 which prevent the transducer 1 from striking the article being tested.

The transducer 1 is connected to an electric circuit through conductors 26, 27 connected to the pins 19, which are passed through the contact bushes 13 and 14 connected are passed through the contact bushes l3 and 14 connected to the differential coils 4,5 (FIG. 5), and the conductors 28, 29 (FIG. 2) connected to the other pins 19, which are passed through the bush contacts 11 and 12 connected to the inductor coil 3.

When replacing the transducer 1, it is necessary to remove the cover 30 of the apparatus together with the guard 25, then to unscrew the nuts 20 from the pins 19, to remove the transducer 1 from these pins to set a new transducer thereon for the other rolled stock or tubes and to assembly the device in a reverse order.

The circuit diagram of the electromagnetic apparatus is given in FIG. 7 wherein F is the electromagnetic apparatus, G is a power supply unit, H is a audiofrequency generator, .I is an amplitude-phase discriminator, K is an electronic amplifier, L is an output device.

The electromagnetic apparatus for detecting defects in rolled products and tubes operates as follows.

If the apparatus is installed, for example, directly in a metallurgical line for producing tubes (not shown in the drawings), these tubes are passed through the guards 24, 25 and the transducer 1 having three coils 3,4 and 5 individually mounted in the grooves C and D of the disks 7 and 8. The second coil 3 being of a higher diameter excites an electromagnetic field of a higher frequency within the active zone of the transducer 1, while the third and fourth coils 4 and 5 disposed at both sides of the coil 3 at a comparatively small distance from each other are used for forming a signal sensitive to the higher frequency field created by the coil 3 and to the field of eddy currents. In case of passing a nondefective portion of the tube through the transducer 1, only signals caused by interference and the unbalance of the coils 4 and 5 are fed from these coils through the conductors 26 and 27, which signals do not form a signal at the output of the apparatus. When a defective portion of the article is passed through the operating zone of one of the coils 4 or 5, a signal appears which is characterized by a definite amplitude and phase and which is modulated by the frequency of the audiofrequency generator H. This signal is applied to the input of the amplitude-phase discriminator J employed for separating the signals by their phase characteristics.

After that the signal is amplified by voltage and power in the electronic amplifier K and is fed to the output device L intended for selection of the signals from the defects and interference by the steepness of their fronts as well as for shaping a control pulse.

The control pulse may be fed to the known devices for automatic rejection of faulty articles from a metallurgical production line into .a storage pocket and, furthermore, for marking the defective places.

Scale and water penetrating into the transducer zone from the controlled rolled products or tubes are not accumulated in the apparatus but are removed through the slot (window) B, thus eliminating a possibility of forming current-carrying bridges and leakage currents causing failures in the operation and reducing the quality of the control.

Furthermore, when controlling the rolled products and tubes by the electromagnetic apparatus having a transducer with three individually mounted coils 3,4 and 5, there are no problems associated with the reliability of the intercoil insulation, while the apparatus itself is extremely low-tension (low-resistance), which fact, in turn, increased the operational reliability of the apparatus used in a process line.

As the differential coils 4 and 5 are individually mounted at a relatively small distance from each other, in the process of passing the rolled products or tubes through the electromagnetic apparatus, the length of the controlled portions is increased due to reduction of the uncontrollable ends of the rolled products or tubes.

We claim:

1. An apparatus utilizing search coils of a transducer for a system for detecting defects in metal tubes moving along the production line of a mill, comprising a hollow housing having coaxial inlet and outlet guards for passing the tube to be tested; a first coil for applying a uni-directional biasing field in the tube to be tested, said first coil being secured in said housing concentrically with said coaxial guards; a framework formed of a dielectric material positioned between the inlet and the outlet guards within said coil, said framework including a pair of ring-shaped covers and a pair of central disks connected at their ends; each said disk having a radial slot extending therethrough and sloped downwardly for discharge of water and scale falling from said tube, said disks being provided with annular grooves in each end, means forming an inner annular channel through interconnection of the central disks, and means connecting thering-shaped covers forming a pair of outer channels which are symmetrical relative to the inner channel and having a smaller peripheral diameter than the peripheral diameter of the groove in the inner channel; a second coil having a rigid ring configuration being positioned in said inner annularchannel and connected for inducing a field from an alternating current and for said bush contacts for fastening said framework of dielectric material to the hollow housing and for connecting the transducer coils to the defect-detecting system. 

1. An apparatus utilizing search coils of a transducer for a system for detecting defects in metal tubes moving along the production line of a mill, comprising a hollow housing having coaxial inlet and outlet guards for passing the tube to be tested; a first coil for applying a uni-directional biasing field in the tube to be tested, said first coil being secured in said housing concentrically with said coaxial guards; a framework formed of a dielectric material positioned between the inlet and the outlet guards within said coil, said framework including a pair of ring-shaped covers and a pair of central disks connected at their ends; each said disk having a radial slot extending therethrough and sloped downwardly for discharge of water and scale falling from said tube, said disks being provided with annular grooves in each end, means forming an inner annular channel through interconnection of the central disks, and means connecting the ring-shaped covers forming a pair of outer channels which are symmetrical relative to the inner channel and having a smaller peripheral diameter than the peripheral diameter of the groove in the inner channel; a second coil having a rigid ring configuration being positioned in said inner annular channel and connected for inducing a field from an alternatinG current and for inducing eddy currents in the tube; third and fourth coils each having the configurations of rigid split rings being positioned in respective of said outer channels and differentially connected for producing a signal sensitive to the A.C.-induced field and to the eddy currents; two pairs of current-carrying bush contacts interconnecting said central disks, one pair of said bush contacts being connected to said second coil and the other pair of said bush contacts being connected to the third and fourth coils; and contact pins extending through said bush contacts for fastening said framework of dielectric material to the hollow housing and for connecting the transducer coils to the defect-detecting system. 